The present invention relates to an all-fiber polyester cloth having relatively large elastic properties of the order of 15% to 20% and without using elastomeric type materials. More particularly, the invention relates to a method of manufacturing such a cloth implementing two-component polyester fibers having a side-by-side structure suitable for developing helical and spiral crimp. The invention also relates to cloth obtained by said method.
The use of textured threads makes it possible to obtain a polyester cloth having a high degree of elasticity, but such use naturally excludes an all-fiber cloth since textured threads are by nature continuous threads. With an all-fiber polyester cloth, elasticity can be conferred by using a certain fraction of elastomeric fibers, and in particular of elastane fibers. Proposals have also been made to use two-component fibers of side-by-side structure, i.e. synthetic fibers having two juxtaposed parts with physical or chemical characteristics that are different, the differences subsequently giving rise to a certain amount of crimping of the fibers. In particular, Rhone-Poulenc Fibres presented a fiber of this type in 1984 under the name X403. It has a side-by-side structure whose two longitudinally-juxtaposed parts are chemically-different polyesters obtained from two different diols. According to the producer, that fiber develops helical and spiral crimping giving it bulk and stretch, like that which is obtained with textured threads, with the exception that the spun fibers, whether pure or mixed, have no stretch; crimping and thus stretch being revealed only during the dyeing or the various heat treatments applied to the cloth. More precisely, Rhone-Poulenc Fibres recommended performing the following succession of operations on the loomstate cloth, namely: washing, heat treatment at 190xc2x0 C. for about 30 seconds, dyeing at 130xc2x0 C., chafing after dyeing, stenter drying, brushing/cropping, and finishing.
However, the Applicant has observed that by complying scrupulously with the above-mentioned recommendations, the resulting cloth does not have elasticity of 15% to 20%, as announced.
The object of the Applicant is to propose a method of manufacture that mitigates the above-specified drawback, i.e. that makes it possible under industrial conditions to obtain an all-fiber polyester cloth that is elastic, containing a certain fraction of two-component side-by-side structure polyester fibers, suitable for developing helical and spiral crimp.
In conventional manner, the method comprises operations of preparing the mixture of fibers, of spinning, of weaving, and of applying various treatments to the cloth.
In characteristic manner, the operations of preparing and spinning lead to a non-extensible thread and the weaving is highly decompacted so as to take account of its potential elasticity, the loomstate cloth being subjected to heat pre-treatment in hot air at a temperature lying in the range 180xc2x0 C. to 190xc2x0 C. under very low tension, prior to performing any conventional treatment in a liquid medium, and in particular washing and dyeing; in addition during all operations subsequent to the heat pre-treatment, tension on the cloth is limited.
Thus, contrary to the recommendations of the producer, it is imperative, according to the Applicant, for the first heat treatment to which the loomstate cloth is subjected to be heat pre-treatment that is performed dry, any preliminary aqueous treatment in hot water of the washing type being to be avoided insofar as that gives rise to a consequent loss of stretch potential of the two-component fibers in the final product.
The dry heat pre-treatment must be followed by taking precautions during subsequent treatment operations to limit the tension exerted on the cloth.
The dry heat pre-treatment preferably consists in using a stenter for a duration of 1 min to 1.5 min, approx., at a temperature of about 185xc2x0 C.
With a 50/50 polyester/wool mixture, in which all of the polyester fibers are of the side-by-side structure, the stenter is used with advance of about 15% and with width at the outlet of the stenter being adjusted to be about 9% smaller than the width of the loomstate cloth.
Furthermore, the Applicant has also observed that the operations of preparing the fiber mixture and of spinning can give rise to a loss in the potential stretch of the cloth. With a conventional polyester/wool cloth, there are initial guiding operations on each type of fiber leading to the formation of wool slivers and of polyester slivers; the fibers are mixed starting from these two types of sliver, known as xe2x80x9ctopsxe2x80x9d, with a re-combing operation integrated in the spinning.
In a manner characteristic of the invention, the fibers are mixed directly on the card and spinning is free from any re-combing operation.
This particular mode of operation has been found by the Applicant by observing that the re-combing operation while spinning leads to a significant drop in the stretch potential of the cloth if insufficient relaxation time is allowed. In practice, it is difficult to guarantee reliably that such rest time will always be complied with, so it has been found appropriate purely and simply to omit the re-combing operation during spinning by using a different preparation route in which the wool and two-component polyester fibers are mixed on the card at the outlet from a mixer fed with bales of stock fiber.